The objective of this collaborative molecular genetic study of asthma is to provide better understanding of the major genes involved in asthma. The project involves the collection of pedigrees of large families, the acquisition of pedigrees of large families, the acquisition of immortalized lymphocytes and/or DNA for analysis of genetic markers and mapping studies, and the conduct of investigations of the association of potential genetic and phenotypic markers with the expression of asthma phenotype(s) within the families being studied.